pipingdesign: Re: Anchor Block Requirement

From: <Geoff>
Date: Wed Oct 02 2002 - 18:02:00 EDT

Tony,

We are in violent agreement on this matter.

Could you comment on a matter posted recently on pre insulated pipe where the skin friction holds the outer shaeth in place and the inner pipe expands and contracts. Do you have any experience in the foam shearing or crushing at changes of direction. The system suppliers believe that there isnt a problem but they perhaps havent dug any up after years of service. Can you believe that the foam has sufficient shear strength as to restrain the inner pipe from moving?

Geoff Stone
--- Tony Paulin <tony@paulin.com> wrote:

<tt>
Thrust Blocks on Underground Piping: 
There are two types of pressurized underground piping systems, those that support axial tension and those that do not. Bell and spigot type end connections do not support axial stress in the pipe and so the end thrust (P times A) must be carried by the soil via an anchor block or the pipe joint will separate. 
 
When a buried pipe is circumferentially welded at each joint such restraint is not needed unless the axial thermal or pressure expansions produce excessive stresses or displacements, usually however, the solution is to permit the expansion, not try to restrain it. 
Anchor blocks on circumferentially welded pipe can be placed to: 
    1) Reduce the stress if the displacement cannot be 
        absorbed or tolerated.  In
Holland peat is used in 
        the area around buried bends to
soften the backfill 
        and permit displacement. Dow also
makes a polystyrene 
        product in several grades that can
be used to perform 
        the same function. Permitting the
displacement is usually 
        the solution in these case. 
    2) Stop displacements in areas where transitions to 
        above ground pipe, or where tie-ins
or other 
        connections exist that cannot
tolerate the movement. 
    3) Where large waterhammer loads are expected to 
        prevent excessive pipe movement. 
 
There are other special conditions, but I don't get the feeling that these cases are being discussed. 
 
----- Original Message ----- 
From: "saeed ahmed" <n2701h@yahoo.com> To: <PipingDesign@yahoogroups.com> Sent: Wednesday, October 02, 2002 11:01 AM Subject: RE: [PipingDesign] Anchor Block Requirement 
 
> 
> Actually there is a caculation which gives us the requirement of
thrust 
block for underground piping at bend. Such bends can be 90 deg or less than 90 degree in underground piping. 
> Saeed. 
>  Geoff Stone DD&D Australia wrote:Saeed, 
> 
> Why do think you need a thrust block? 
> 
> Geoff Stone 
> --- saeed ahmed wrote: 
> 
> 
> --------------------------------- 
> 
> 
> 
> 
> 
> 
> 
> Thanks Geoff Stone for the reply. 
> 
> 
> 
> Iam talking about thrust block requirement in underground piping at
bend. 
> 
> 
> 
> Saeed. 
> 
> 
> 
> 
> 
> Steve McKenzie wrote:Hi Geoff 
> 
> 
> 
> I use them on steel lines where water hammer is an issue. 
> 
> 
> 
> Cheers 
> 
> 
> 
> Steve McKenzie 
> 
> 
> 
> -----Original Message----- 
> 
> From: Geoff Stone DD&D Australia [mailto:blenrayaust@yahoo.co.uk] 
> 
> Sent: Monday, September 30, 2002 9:37 AM 
> 
> To: PipingDesign@yahoogroups.com 
> 
> Subject: Re: [PipingDesign] Anchor Block Requirement 
> 
> 
> 
> 
> 
> Saeed, 
> 
> 
> 
> Please provide more details as it is difficult to understand why you
are 
> 
> considering an anchor block for underground piping that is welded? 
> 
> Anchor blocks are sued for rubeer ring jointed ssytems such as ductile 
iron 
> 
> and 
> 
> thermoplastics but not a welded steel pipe. 
> 
> 
> 
> Geoff Stone 
> 
> --- n2701h wrote: 
> 
> 
> 
> 
> 
> --------------------------------- 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> In calculating the anchor block requirement at  underground 
> 
> piping 
> 
> 
> 
> 
> 
> bend,there are two variable involved ,one is tie-in temperature and 
> 
> 
> 
> the other is allowable piping deflection.What should be the critaria 
> 
> 
> 
> taken in the calculation? 
> 
> 
> 
> 
> 
> 
> 
> With thanks 
> 
> 
> 
> Saeed 
> 
> 
> 
> n2701h@yahoo.com 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Texas Flange - a good source for information on industrial flanges,
all 
> they 
> 
> ask is for referrals for designs they help with. 
> 
> 
> 
> 877-610-8924. 
> 
> 
> 
> www.texasflange.com 
> 
> 
> 
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> 877-610-8924. 
> 
> www.texasflange.com 
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> Design Detail and Development (a division of Blenray Pty Ltd) 
> We specialise in pipe network and waterhammer analysis, pipe stress 
analysis, the design of buried pipelines and thermoplastic pipe systems. 
> Local tel 0402 35 2313 fax 02 8850 2313 
> Overseas tel 61 402 35 2313 fax 61 2 8850 2313 
> Mail Address PO Box 1351 Castle Hill NSW 1765 Australia 
> 
> __________________________________________________ 
> Do you Yahoo!? 
> New DSL Internet Access from SBC & Yahoo! 
> http://sbc.yahoo.com 
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> 
> Texas Flange - a good source for information on industrial flanges,
all 
they ask is for referrals for designs they help with. 
> 877-610-8924. 
> www.texasflange.com 
> ===================================================== 
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> Texas Flange - a good source for information on industrial flanges,
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> 877-610-8924. 
> www.texasflange.com 
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<tt>
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Design Detail and Development (a division of Blenray Pty Ltd) We specialise in pipe network and waterhammer analysis, pipe stress analysis, the design of buried pipelines and thermoplastic pipe systems. Local tel 0402 35 2313 fax 02 8850 2313
Overseas tel 61 402 35 2313 fax 61 2 8850 2313 Mail Address PO Box 1351 Castle Hill NSW 1765 Australia

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New DSL Internet Access from SBC & Yahoo! http://sbc.yahoo.com Received on Wed Oct 02 18:02:00 2002

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